In all the talk about Canada's lofty house prices, it's easy to overlook the fact that roughly one-third of the country's households are rented.

And a new rental housing index, which uses 2016 census data, shows renters are suffering from a much more widespread affordability problem than homeowners.

For those who own, affordability issues have mostly been concentrated in Toronto, Vancouver and their surrounding areas; many other Canadian cities, as well as rural areas, remain affordable for buyers.

Not so for renters. The rental housing index shows extremely unaffordable housing costs affecting numerous mid-sized and small cities, as well as rural areas, across Canada. The index's map shows an archipelago of crisis-level rental costs from Greater Vancouver to Alberta's oil patch to wide swaths of the Maritimes.

Canadian Rental Housing IndexThis heat map from the Canadian Rental Housing Index shows "severely unaffordable" rental costs are not limited to Canada's major cities.

The data shows that, nationally, four in 10 renters are spending more than 30 per cent of their income on rent and utilities. That's the cutoff level for what Canada Mortgage and Housing Corp. considers affordable.

And nearly one in five renters — 18 per cent — are putting half or more of their income toward rent and utilities. That's a "crisis level" of spending that puts people "at risk of homelessness," says the B.C. Non-Profit Housing Association (BCNPHA), which — together with Vancity Credit Union — developed the index.

That rate isn't actually much higher in the pricey centres of Toronto and Vancouver, where 23 per cent of renters hand over more than half their income to the landlord.

And these days, there may be no escape.

In earlier times, finding a more affordable rental home was often as simple as moving farther out into the suburbs. But housing costs in outlying areas are catching up to urban areas, BCNPHA says.

The data from the index shows "the suburbanization of poverty, where major affordability challenges are just as prevalent in the surrounding communities as they are in those urban centres," said Marlene Coffey, executive director of the Ontario Non-Profit Housing Association, in a statement.

Home ownership on the decline

The 2016 census, from which the housing index derives its data, shows that the home ownership rate in Canada declined between 2011 and 2016, as rising house prices forced some first-time buyers to delay their purchase.

That period marked "the first time in a generation that the rate of Canadian renters has outpaced the number of Canadians buying a home, and speaks to the need to increase the supply of affordable housing," said Jeff Morrison, executive director of the Canadian Housing and Renewal Association, in a statement.

With more people staying longer in rental housing, rental rates have started to accelerate in recent years. Housing developers have reacted to an extent, with a jump in the number of purpose-built rental buildings being put up.

But most observers would agree that what's being built by developers is not nearly enough, and as long as selling condos is the more profitable activity (which it continues to be), the private sector will likely do little to help the situation.

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Many affordable housing advocates, as well as some economists, have been arguing for years that the affordability problem — both for renters and owners — stems in part from the fact that governments have backed away from building social housing.

"Lessons can be learned from Quebec, which has better rental housing affordability relative to any other province or territory in the country," BCNPHA says. While many governments across Canada had backed away from affordable housing programs by the 1990s, Quebec continued with its own.

And now, with housing affordability becoming a political issue, other governments are listening. The federal Liberals recently reached a deal with all provinces and territories except Quebec to spend more than $16 billion over a decade on the construction of 50,000 new affordable housing units and the renovation of another 60,000.

Starting in 2020, that money will also provide a $4-billion benefit that will see some 300,000 households receive financial support for their housing costs.

Earlier on HuffPost Canada:

"We welcome all the investment from the national housing strategy and we think it's a great step, but we don't think it's sufficient to cover the scope of the problem," said Brian Clifford, policy manager at BCNPHA, in an interview with HuffPost Canada.

Clifford singled out Ontario as being in particular need of additional measures to address housing affordability.

"The data clearly shows Ontario has the worst problem out of any province or territory and they need significant investment into affordable housing."

In a unique move, the British Columbia government announced plans to allow cities to zone certain areas as rental-only, in the hopes of nudging developers to ramp up the supply of rental housing.

Clifford described that as a "fantastic policy measure, and one that will help with the overall affordability crisis" in British Columbia.